Yorke says the dress will be made by an "little-known" designer -- read: not Issa, one of Middleton's favorite labels:

There's indication that Catherine has gone for a young, 'little-known,' British designer. When the name is officially announced, it will come as a surprise to many, and the designer will then be known around the world. For clues on the identity, I suggest looking at those who have made dresses for Catherine, her sister Pippa, and her mother Carole.

In addition to Issa, Yorke also insists that Bruce Oldfield -- who designed some of Princess Diana's dresses -- is an unlikely candidate, since Middleton is already wearing Diana's engagement ring, so it's unlikely she'd opt for more references to the late princess.